This invention is directed generally to circuit breakers, and, specifically, to an arc stack for a circuit breaker.
A circuit breaker generally contains an arc stack assembly which has the purpose of receiving and dissipating electrical arcs that are created when a movable contact separates from a stationary contact.
One particular type of arc stack includes a number of arc plates which are offset at equal distances from one another, being supported on each side by a insulating plate. The plates are generally rectangular in shape, identical to one another, and interconnected. Each plate has an arc throat that creates a path for the blade to open and to close whenever the circuit breaker is tripped and reset, respectively. The path is formed by laterally offsetting the identical arc plates relative to one another in the same direction, tracing the imaginary radius that the blade creates when opening and closing.
A drawback of this type of arc stack is that it is sometimes difficult to manufacture, particularly when dealing with circuit breakers that are relatively small in size where space is tight. Easy and reliable automated installation of the arc plates to the insulating plate would greatly increase efficiency and productivity while lowering production costs.
Another drawback typically encountered in this type of arc stack is that molten debris, which is created when the circuit breaker interrupts current, may interfere with internal components of the circuit breaker by either welding internal parts together or by jamming the operating mechanism.
Accordingly, it is an object of this invention to catch and solidify molten debris that is created when the circuit breaker interrupts current, preventing the debris from welding together internal parts of the circuit breaker or from jamming operating parts of the circuit breaker.
It is another object of this invention to make the connection for the arc plates easier and more reliable, therefore, reducing the labor required to assemble the circuit breaker.
In accordance with a preferred embodiment of the invention, an arc plate assembly for a circuit breaker is provided. It includes a pair of parallel spaced vertically oriented insulative mounting plates having mounted thereon a set of arc plates arranged in an arcuate array generally tracing the arcuate path of movement of a circuit breaker moveable contact blade. A baffle plate is mounted between the insulative mounting plates and positioned above the uppermost arc plate in the set for blocking arc-formed debris from projection into the operating mechanism of said circuit breaker The arc plate assembly baffle plate is preferably mounted at an angle such that it defines with the uppermost arc plate a wedge-shaped volume for catching and solidifying molten arc-formed debris. The baffle plate is preferably mounted at a downward inclination toward the uppermost arc plate.
In accordance with a further embodiment, an arc plate assembly is provided in which the baffle plate and said arc plates are provided with mounting tabs extending toward the insulative mounting plates. The mounting plates are provided with mounting apertures, and the mounting tabs are passed through said apertures and crimped against the exterior surfaces of said mounting plates.
According to a further preferred embodiment, an arc plate assembly for a circuit breaker is provided with a pair of parallel spaced vertically oriented mounting plates having mounted thereon a set of arc plates arranged in an arcuate array generally tracing the arcuate path of movement of a circuit breaker moveable contact blade, with the arc plates being so mounted by tabs extending through apertures in the mounting plates and being crimped against the exterior surfaces of the mounting plates. Further, in accordance with the invention, a method is provided for blocking arc-formed debris projected from the vicinity of an arc plate array in a circuit breaker toward the operating mechanism of the breaker which includes interposing a downwardly extending baffle plate at the top of the arc plate array between the array and the mechanism.